ASP.NET VB throwing a strange error

Hello,

Coding along I wanted to first detect if a field in a datareader record was a certain value then go into a loop to process that and any other records as:

' process any full siblings
try
if dtr.item("RelType") = 3 then
DisSib += "<p style='left-margin = 1em'>Full Siblings</p>"
do while dtr.item("RelType") = 3
DisSib += _
"<p style='left-margin = 2em'><a href='critter_details.aspx?id=" &amp; dtr.Item("C.Animal_ID") &amp; "'>" &amp; dtr.Item("Name") &amp; "</a> " &amp; _
GetReg(1, dtr.Item("Registrations")) &amp; " " &amp; _
dtr.Item("Color") &amp; " " &amp; _
dtr.Item("Gender") &amp; " " &amp; _
dtr.Item("Birthdate").Year &amp; "</P>"
dtr.Read()
loop
end if
catch e as exception
ErrorNotification(e, "Error in display sibling routine")
exit function
end try

The error it throws is:

System.InvalidOperationException: No data exists for the row/column. at System.Data.OleDb.OleDbDataReader.DoValueCheck(Int32 ordinal) at System.Data.OleDb.OleDbDataReader.GetValue(Int32 ordinal) at System.Data.OleDb.OleDbDataReader.get_Item(String name) at DunCity.General.DisSib(Int32 i) in E:\web\duncitycom0\htdocs\critter_details.vb:line 229
Error number = 5
Source = System.Data
Description = No data exists for the row/column.

Indicating the line in red.

Has anyboy seen this error and have a suggestion?

Thanks,
Jim

 

Hello Joel!


Thanks for your replies.


In my code I check for the existance of records and exit if they don't exist before I hit the code shown. My question is, why can I refer to the column value just 2 lines before without the page blowing up on that referance? I would think (here's where I get dangerous) that I can refer to that coloumn as many time as I choose and expect the same results as long as I don't issue a read "dtr.read()". I have never heard of "distructive reads" in an ASP.NET context, but you never know.


What do you think?


Jim

 

You need to check to see if the record exists inside the loop. dtr.Read() will return False when there is no record. inside your loop you weren't checking the value returned.


Joel Thoms

DiscountASP.NET
http://www.DiscountASP.NET

 

What is your query? Is it possible after a certain number of records the RelType column doesn't exist?

It could possibly be complaining about a null value, try this....

do while (Not IsNothing(dtr("RelType")) AndAlsodtr.item("RelType") = 3)



Joel Thoms

DiscountASP.NET
http://www.DiscountASP.NET

 

My answer is totally wrong... I just noticed what you are doing. and the reason you are getting that error is because the column does not exist...

You need to change this...

dtr.Read()

To This...

If (Not dtr.Read()) Then Exit Do


Joel Thoms

DiscountASP.NET
http://www.DiscountASP.NET

 

AH HA! Soit was failing not on the first iteration but on a subsequent trip when I hit EOF. I really appreciate your second set of eye on this issue Joel. Thanks.</o>
</o>
Slightly embarrassed,</o>
Jim</o>